Conventionally piezo stacks consist of many individual actuator or sensor layers. The structure is comparable with ceramic capacitors. Initially, at one edge of the actuator/sensor in each case all electrodes of a pole are connected to each other by a printed metal strip. With a capacitor the connecting lead can now be soldered onto this contact. However, since the actuator/sensor changes its length, stress cracks occur in the contacted areas. This interrupts the contacting. For contacting of piezo stacks the contacting is therefore connected flexibly to the connecting leads at as many points as possible. To this end what is known as a wire harp consisting of many individual wires is soldered onto the stack electrodes and connecting lines. To insulate the wire harp and the actuator or sensor electrodes from each other the actuator/sensor is coated with insulation material. Subsequently the actuator/sensor is also packed into an elastic encapsulation to stabilize the connecting leads and to protect the wire harp.
The disadvantage is that the stress fractures in the contacting area caused by the changes in length of the actuator or sensor cannot be excluded completely.